This invention relates to solenoid operated fuel injectors of the spherical valve ball type used to control the injection of fuel into an internal combustion engine;
It is known in the fuel injection art to utilize a spherical valve ball within a solenoid operated fuel injector to close a fuel passageway in the injector. In such injectors, it is common to fabricate a flat on the ball valve and use the ball in combination with a collar that provides an annular cradling surface for the ball. A spring disc interfaces with the ball and urges the ball into an open position. Fuel is communicated around an armature and through the spring disc to establish fuel flow when the ball is in an unseated position. The ball must be guided to center itself on a seat of the fuel passageway and the armature requires a surface to keep the ball at least proximately concentric within the axis within the radial confinement imposed on the ball by the tip end of the armature.
With such assemblies, the dynamic flow rate of the fuel is set through the spring rate and selecting the spring becomes critical. These injectors require a non-magnetic plug in the bottom of their armatures to reduce wear and have a coil that is contacted by the fuel.
The present invention provides a solenoid actuated fuel injector having a simplified construction wherein a return spring biases a spherical valve ball onto a seating surface and, upon actuation of a solenoid coil, an armature picks the valve ball off the seat. When the coil is deactivated, the armature releases the ball, allowing the ball to return to the center of the seating surface.
According to the invention, the solenoid actuated fuel injector comprises a housing having a longitudinal axis and a valve body fixed to the housing. The valve body has a cylindrical sidewall coaxial with the housing longitudinal axis that laterally bounds the interior of the valve body. A valve seat at one end of the valve body includes a seating surface facing the interior of the valve body. The seating surface includes a fuel outlet opening centered on the axis and is in communication with means for conducting pressurized fuel into the valve body against the seating surface. The seating surface may be frustoconically shaped or of a concave shape.
A spherical valve ball within the injector is moveable between a seated position, wherein the ball is urged against the seating surface to close the outlet opening against fuel flow, and an open position, wherein the ball is spaced from the seating surface to allow fuel flow through the outlet opening. Biasing means, such as a coil spring, in the valve body is provided for biasing the valve ball toward the seated position.
An armature axially moveable in the valve body includes valve ball capturing means at an end proximate the seating surface. The valve ball capturing means engages with the ball outer surface adjacent the seating surface. A solenoid coil is operable to draw the armature away from the seating surface, thereby moving the valve ball to the open position and allowing fuel to pass through the fuel outlet opening. Deactivation of the solenoid coil allows the biasing means to return the valve ball to the seated position against the seating surface and to align itself in the seated position, thereby closing the outlet opening against the passage of fuel.
The armature includes an axially extending through-bore that allows fuel to pass and receives the valve ball. A fuel passage extending from the through-bore to an outer surface of the armature allows fuel to be communicated around the valve ball. The valve ball capturing means engages the ball at a diameter of the ball that is less than the major diameter of the ball and at a position between the major diameter of the ball and the seating surface. Herein the valve ball capturing means is an end of the armature wherein the through bore has a reduced diameter less than the major diameter of the ball. Alternatively the capturing means may be a plurality of fingers extending from the armature.
A method of assembling the solenoid actuated fuel injector comprises the steps of:
assembling a valve group subassembly;
assembling a coil group subassembly;
assembling together the valve group sub-assembly and coil group subassembly; and
snap fastening together cooperating snap features on the valve group and coil group subassemblies.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.